The present invention disclosed herein relates to a novel structural electric device having improved safety, and more particularly, to a novel structural electric device devised to resolve several issues regarding heat generation, ignition, and explosion, which may be caused by a sharp needle-shaped object penetrating an electric device.
A secondary battery is classified into a cylindrical type, a polygonal type, and a pouch type according to packaging types and manufacturing methods and has been developed and manufactured until now.
Measures to deal with an issue of a sharp needle-shaped object penetrating into a secondary battery or an issue occurring during a test for a needle-shaped penetration in a secondary battery may vary according to packaging types and manufacturing methods. However, most of the measures may not provide reliable solutions. This is because there is no sure solution to basically resolve a short phenomenon between electrodes that constitute a battery.
As a representative method for resolving the above short phenomenon, a method of improving the stability for needle-shaped penetration in a secondary battery by coating an isolation layer with ceramic material is introduced. However, a new approach is required as the size of a secondary battery is increased and its energy density becomes higher. However, the above method with the coated isolation layer may not obtain basic stability easily.
Moreover, it is a common situation that explosion occurs while metal penetrates a secondary battery under an abnormal condition or a safety test such as a penetration test for a secondary battery is in progress. Based on the situation, the explosion cause may be inferred as follows.
If a penetrating material has high electrical conductivity, it causes a short between positive and negative electrodes in a secondary battery. Also, due to this, current flows internally. As a result, a deterioration phenomenon of the secondary battery occurs easily and furthermore an ignition or explosion phenomenon occurs also.
Thus, in order to prevent dangerous situations such as abnormal explosion of a secondary battery before happening when a needle-shaped object penetrates the secondary battery, studies on preventing the above dangerous situations basically and improving the stability of the secondary battery are required.